High-resolution tracking of materials used in industrial production processes is required for comprehensive material control, inventory control (or stock control), process control, logistics control, quality control and pollution control. These controls ensure that materials used in industrial production processes are available in the required place, at the required time, in the required quantities, and in the required quality, as well as ensuring that materials are properly accounted for from acquisition and processing, to use and disposal.
Public and private sector demand for high-resolution tracking of industrial process materials has been heightened by concerns about terrorist misuse of explosives and agrochemicals, quality and contamination of food/medicine/fuel/feed, illicit substitution of inferior materials, liability for defective products and built structures, price and availability of commodities, and pollution of the environment.
Interest in high-resolution tracking has also been driven by life-cycle thinking about materials and products. The life-cycle concept is a “cradle-to-grave” approach which recognises that materials and products have economic and environmental impacts as they pass through the life-cycle stages of raw material acquisition, processing, manufacturing, formulation, transportation, distribution, use, reuse, maintenance, recycling, disposal and waste management. Intense material tracking is required for a comprehensive life-cycle inventory, even for a simple product made of a single raw material in one or two manufacturing steps.
It is difficult to track industrial process materials that are standardised, undifferentiated, substitutable, interchangeable, batch-processed in essentially identical form, and available in bulk or from a variety of sources. Examples of such materials include primary commodities, such as agricultural and mineral products, and processed commodities, such as manufacturing materials, building materials and industrial chemicals. In practice, the low inherent visible identity of these materials defeats high-resolution tracking.
Luminescent marking has been proposed for identifying or authenticating high-value articles or materials and in particular security documents such as passports, banknotes, credit cards, cheques, as well as articles such as jewelry, vehicles, electronic goods, etc. However, prior luminescent marking systems require either relatively high amounts of luminescent materials to make detection reliable in ambient light or, when using trace amounts of luminescent materials, sophisticated and bulky laboratory spectrometers for detecting luminescence. High concentrations of luminescent materials are not practicable or cost-effective for tracking industrial process materials which are generally low-value commodity materials, typically mass-produced and sold in bulk. Furthermore, the use of laboratory detection equipment often requires detailed sample preparation by a trained analytical chemist and is not amenable to high-throughput mass screening of samples for off-site applications.